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通过对纯钛(TA2)表面改性获得不同静态接触角的冷凝表面,并对水蒸气在各试样表面的传热特性进行了可视化实验研究。实验结果表明,蒸汽在原始表面为液滴和沟流状液膜共存的混合冷凝,在氢氟酸刻蚀表面为膜状冷凝,传热性能降低为原始表面的30%以下,而在双氧水氧化表面及氢氟酸刻蚀后再双氧水氧化表面则为明显的滴状冷凝,相应传热性能也有明显提高,约为原始表面的1.3~1.6倍,且经两步处理表面强化冷凝效果更为明显。通过对试样表面显微形貌的观察和分析指出,冷凝表面微观形貌的改变是导致各试样表面静态接触角和冷凝形貌存在差异的主要原因。
Through the modification of the surface of pure titanium (TA2), the condensation surfaces with different static contact angles were obtained, and the heat transfer characteristics of water vapor on the surface of each sample were visualized. The experimental results show that the steam is mixed and condensed on the original surface by the coexistence of liquid droplets and channel liquid film. The film is condensed on the hydrofluoric acid etching surface and the heat transfer performance is reduced to below 30% of the original surface. Surface hydrogenation and hydrofluoric acid followed by hydrogen peroxide oxidation of the surface is obvious droplet condensation, the corresponding heat transfer performance has improved significantly, about the original surface of 1.3 to 1.6 times, and after two steps of the surface enhanced condensation more pronounced . By observing and analyzing the microstructure of the sample surface, it is pointed out that the change of the micro-morphology of the condensing surface is the main reason that causes the static contact angle and the condensation morphology of the sample surface to be different.